TWI842995B - Detection system for use in a multi-beam charged particle system and particle beam system - Google Patents

Abstract

What is described is a particle beam system, comprising a particle source, configured to produce a first beam of charged particles. The particle beam system comprises a multiple beam producer, configured to produce a plurality of partial beams from a first incident beam of charged particles, which partial beams are spaced apart spatially in a direction perpendicular to a propagation direction of the partial beams, wherein the plurality of partial beams comprises at least a first partial beam and a second partial beam. The particle beam system comprises an objective, configured to focus incident partial beams in a first plane in such a way that a first region, on which the first partial beam is incident in the first plane, is separated from a second region, on which a second partial beam is incident. The particle beam system comprises a detector system, comprising a plurality of detection regions and a projective system, wherein the projective system is configured to project interaction products, which leave the first plane due to the incident partial beams, onto the detector system. The projective system and the plurality of detection regions are matched to one another in such a way that interaction products emanating from the first region of the first plane are projected onto a first detection region of the detector system and interaction products emanating from the second region of the first plane are projected onto a second detection region, which differs from the first detection region. Furthermore, the detector system comprises a filter device for filtering the interaction products in accordance with their respective trajectory.

Description

Detector system and particle beam system for multi-beam charged particle beam system

The present invention relates to a particle beam system operating with a plurality of particle beams.

WO 2005/024881 A2 discloses a multi-particle beam system in the form of an electron microscope system, which operates using a plurality of electron beams so as to simultaneously scan an object to be inspected by beam focusing of the electron beams. The beam focusing of the electron beam is generated by directing an electron beam generated by an electron source to a porous plate having multiple apertures. Some of the electrons of the electron beam strike the porous plate and are absorbed by the plate, and other parts of the electron beam pass through the apertures of the porous plate, so that an electron beam is formed in the electron beam path after each aperture, and the cross section of the electron beam is defined by the cross section of the aperture. Furthermore, a suitably selected electric field provided in the upstream of the electron beam path and/or in the downstream of the porous plate is directed to each aperture in the porous plate, each aperture acting as a lens on the electron beam passing through the aperture, so that the electron beam is focused in a plane at a distance from the porous plate. The plane forming the focus of the electron beam is imaged by subsequent optical equipment on the surface of the object to be inspected, so that the individual electron beams impinging on the object are focused into a main electron beam. Backscattered electrons or secondary electrons originating from the object are generated here, which form a secondary electron beam and are guided to a detector by other optical equipment. At the detector, each of the secondary electron beams impinges on a separate detector element, so that the electron density detected therebetween provides information about the position of the object at which the corresponding primary electron beam was incident on the object. The primary electron beam is systematically scanned across the surface of the object to produce an electron microscopic image of the object in the manner conventionally used for scanning electron microscopes.

The object of this patent application is to develop such a multi-beam particle beam system and in particular to further improve the contrast generated within such a multi-beam particle beam system. A further object is to specify the developed method for the particle optical inspection of an object.

The specified object can be achieved by means of a detector system having the features as in the subsequent patent claims. Advantageous specific embodiments are derived from the features of the independent patent claims.

According to a specific embodiment, the particle beam system includes a particle source, which is configured to generate a first charged particle beam. Further, the particle beam system includes a multi-beam generator, which is configured to generate a plurality of particle beams from a first incident beam of charged particles, so that the particle beams are spatially separated from each other in a direction perpendicular to the propagation direction of the partial beams. Here, the plurality of partial beams include at least a first partial beam and a second partial beam. The particle beam system further includes an objective lens, which is configured to focus the incident partial beams in a first plane, so that a first area on which the first portion is incident in the first plane is separated from a second area on which the second partial beam is incident. Further, the particle beam system includes a detector system including a plurality of detection areas and a projection system. The projection system is arranged to project the interaction products leaving the first plane due to the incident partial beam onto the detection regions of the detector system. Here, the projection system and the plurality of detection regions are matched to each other so that the interaction products emanating from the first region in the first plane are projected onto a first detection region of the detector system and the interaction products emanating from the second region in the first plane are projected onto a second detection region. Here, the second detection region is different from the first detection region. Furthermore, the detector system comprises a filtering device for filtering the interaction products according to their individual tracks.

By suitable filtering of the interaction products according to their individual trajectories, the contrast in the image created by merging the output signals of the detector system can be increased so that the many detection areas form an overall image. Here, the filtering should not be limited to masking or suppressing interaction products whose trajectories extend in outer regions far from the optical axis of the projection system.

The charged particles may be electrons or ions. In particular, the interaction products may be secondary electrons or backscattered electrons. However, the interaction products may also be primary particles which undergo a reversal of motion due to the deceleration potential between the objective and the object without physical scattering processes occurring between the primary particles and the object.

In a specific embodiment, the filter device has a plurality of first detection fields, which are associated with the first detection region. Furthermore, the filter device has a plurality of second detection fields, which are associated with the second detection region. Here, each of the first and second detection fields is embodied to detect the impact of the interaction products on the individual detection field in a manner independent of the impact of the interaction products on the other detection fields. Expressed differently, the detector has a plurality of detection fields for each detection region, which in each case detect each interaction product separately. Such an instrument is known from light microscopes, from documents US8705172B2 and DE102010049627 A1 and from the not yet published German patent application No. 10 2013 218 795.5.

The particle beam system may further comprise a controller which is embodied to individually read and process the detector signals from the plurality of detection fields of a relevant detection area. By evaluating the relevant detector signals resulting from the many detection fields, important additional information can be obtained. By way of example, analysis of the detector signals of each detection field makes it possible to establish whether the relevant main partial beam is focused incident on an object surface, i.e. whether the object surface overlaps with the first plane at the position of the incident partial beam. This information can then be used to actuate an automatic adjustment system, such as an automatic focus system, a detector adjustment system or a filter adjustment system, so that the partial beams are ideally focused on the surface of the object. Furthermore, at the location where the relevant partial beam is incident on the object, additional information about the topology of the object under inspection can be obtained by comparing the detector signals of the detection fields belonging to the same detection area. Furthermore, the detector signals belonging to the plurality of detection areas or to the entire image are averaged, thus obtaining information about the tilt of the sample within the average detection area (object area) on the surface of the object. Furthermore, within the region on the object surface, the overall shape of the object, as defined by the evaluation detector signals, can be determined by evaluating the detector signals belonging to the plurality of detection regions, and this information can be used to correct a focus and/or correct aberrations in the object regions adjacent to the evaluation object region.

In a further specific embodiment, the detection system may additionally comprise an element for generating dispersion. The element generates the dispersion, which then causes the interaction products associated with a detection area to separate according to their individual kinetic energies. By comparing the detector signals belonging to the detection fields in the same detection area, the kinetic energy of the interaction products when they emerge from the object can be reduced. In this way, a voltage contrast can be generated. Here, the voltage contrast should also be understood as the different potentials at which second electrons emerge from the object area with different charges. An example of this is a contact hole in a semiconductor structure, which establishes contact between different planes of the conductor track structures. If there is no connection between the two planes in such a contact hole, irradiation with charged particles such as electrons will lead to charging in the contact hole, since the charge cannot dissipate. The inelastic scattered particles (such as electrons) or second electrons then start from a different potential than in the case of the contact hole in contact. The result is that these electrons can be distinguished due to their different kinetic energies, and due to the different trajectories caused by the element that generates the dispersion, which allows the detection of uncontacted contact holes at significantly higher speeds, since the signal-to-noise ratio is greatly increased.

In addition to the embodiment with a dispersion-generating element, the filter device can also be a dispersion-generating imaging energy filter. The detected interaction products can be separated and selected according to their kinetic energy by means of this energy filter. This embodiment can also be used to generate a voltage contrast.

According to a further specific embodiment, the projection system comprises a staggered plane and the filtering device is embodied as a light bar arranged in the vicinity of the staggered plane. In particular, the light bar has an annular aperture. What can be achieved by means of the annular light bar is that only those interaction products that emerge from the inspected object within a certain virtual starting angle range are detected. Under the annular light bar, a selection can be made according to which vector component of the initial velocity of the interaction products emerging from the object is parallel to the object surface. As a result, additional information can be obtained about the object surface topology or the material on the object surface at the position on which the relevant partial beam is incident. In particular, the energy distribution of the interaction products passing through the light bar can be partially filtered by the annular light bar. Since the energy distribution of the interaction products, in particular in the case of second electrons as interaction products, depends among other things on the local surface potential and the number of emitted second electrons, i.e. the atomic mass number at the position at which the second electron emerges from the object, additional information can be obtained about the material composition of the object at individual positions on the surface of the object, and even assuming the sample surface.

According to a further specific embodiment, the projection system may comprise a plurality of particle beam lenses arranged one after another in sequence, producing at least two intersecting planes that are connected in succession to each other. Then, a respective light bar may be arranged in each of the at least two intersecting planes. By way of example, a first light bar may have a central aperture through which only interaction products may pass, whose trajectories extend sufficiently close to the optical axis of the projection system. Using such a "bright field light bar", interferences between many detection areas can be avoided. Expressed differently, with the aid of the "bright field light bar", it can be avoided that interaction products emerging from a first area of the first plane impinge on a detection area associated with a different area in the first plane. Once again, a light bar with an annular aperture can be arranged in the second intersecting plane. Similar to the embodiments already described above, it is possible to obtain additional information about the atomic mass numbers on the surface of the object and/or to generate additional topological contrasts. This is preferably performed using a dark field lightbar.

By changing the focal length of the particle beam lens, the filtering effect obtained by the light barrier can be changed. Therefore, in a further specific embodiment, the focal length of the particle beam lens can be changed.

The particle beam lens can be implemented as a magnetic lens or an electrostatic lens, or can be implemented as a combined lens with superimposed magnetic and electrostatic fields.

According to a further specific embodiment, the particle beam system further comprises a beam deflection system, which is specifically implemented to deflect the first particle beam and the second particle beam perpendicular to their propagation direction. In this case, the controller is further specifically implemented to merge the detector signals (belonging to different partial beam deflections) of many detection areas to form an image. By deflecting the partial beams, the entire first area can be scanned by each partial beam, and the image information generated by the plurality of partial beam scans can be merged to form a complete image.

According to a further specific embodiment, the present invention is a method for microscopic particle inspection of an object, comprising the following steps: ● irradiating the object simultaneously with a primary beam of charged particles in a plurality of mutually separated field regions, ● collecting interaction products emitted from the object due to the incident primary particle beam, ● projecting the interaction products onto a plurality of detection regions of a detector, so that the interaction products emitted from two different field regions are projected onto different detection regions of the detector, and ● filtering the interaction products in a manner according to their individual trajectories.

In particular, the products of these interactions are filtered based on their kinetic energy.

As already further explained above, in a specific embodiment, the filtering of the interaction products is performed for each detection area by means of a detector comprising a plurality of mutually independent detection fields sensitive to the interaction products. In this case, the signals of the detection fields belonging to the same detection area can be evaluated relative to one another in order to produce images with improved voltage contrast, improved topological contrast or improved material contrast, for example. Furthermore, edges can be emphasized by a specific calibration or by establishing a height profile of the object surface.

In a further specific embodiment, the particle beam system operates in the so-called reflection mode for a method of microscopic particle inspection of an object. In this method, an electrostatic potential is applied to the object to be inspected, which potential substantially corresponds to the potential of the particle beam generator (particle source). After the electrostatic potential is applied to the object, the primary particle beams are decelerated according to a static reflector to zero kinetic energy before reaching the object, but in the direct vicinity of the object surface, and are accelerated in the reverse direction, i.e. in the direction back to the objective lens. The particles that have undergone reverse motion due to the electrostatic potential of the object are concentrated, and the concentrated charged particles are substantially projected onto a plurality of detection areas of a detector, so that the charged particles collected from two different field areas in the plane of the object are projected onto different detection areas of the detector. In a specific embodiment of the method according to the present invention, filtering is performed according to the trajectory of the collected particles. Here, the concentrated particles are filtered for each detection area by means of a detector that includes a plurality of independent detection fields sensitive to the concentrated particles in each detection area.

When operating the particle beam system in the reflection mode for the examination of non-conductive objects, local charging of the object due to the incident main beam can be almost completely avoided if the radiation parameters are suitably chosen, since the primary particles of the partial beam do not penetrate into the object. If the object potential changes, the object potential of the primary particles falling on the surface of the object with vanishing kinetic energy can be determined. As a result, the potential of the object charge can be determined. If this is performed at a number of different points on the surface of the object, the potential profile in the vicinity of the object surface can be determined. As a result of the filtering of the interaction products as described above, it is further possible to determine the trajectories of the interaction products. The trajectories allow to infer the form of the local potential profile in the vicinity of the object surface and from this the local topology of the object surface. After the "non-contact" sensing of the surface, the charge compensation method can be used to distribute the charge. In particular, by changing parameters such as the object potential or the focus position of the multi-beam particle beam system, the sample topology can be determined with high accuracy from a plurality of data records. Therefore, the method can also include the steps of changing the object potential, determining the potential shape in the vicinity of the object surface, and determining the local topology of the object surface from the local potential shape in the vicinity of the object surface.

In a further specific embodiment of a method for performing microscopic particle inspection of an object using a multi-particle beam system, the interaction products emitted from the object due to the incident primary beam are initially collected with a first suction field and projected onto a plurality of detection regions of a detector, so that the interaction products emitted from two different field regions are incident on different detection regions of the detector. Therefore, the interaction products emitted from the object due to the incident primary particle beams are collected with the aid of a second suction field different from the first suction field. The interaction products collected by the second suction field are then also sequentially projected onto a plurality of detection regions of a detector, so that the second particles emitted from two different field regions of the object are projected onto different detection regions of the detector. The detector signals belonging to different suction fields but within the same detection area are then combined computationally, thus generating a data signal full of the topological effects of the object, which is then used to generate and depict the image. This method can be performed similarly for three, four or more different suction fields in order to achieve higher accuracy when combined computationally. If the suction field can enter the object, this method can also be used to image structures beneath the surface of the object, which are not visible in the individual images.

In the above method, in which interaction products are detected in different inhalation fields, a filtering of the interaction products according to their individual trajectories can also be additionally performed before their detection. As described above, the filtering can be carried out by Fourier filtering in staggered planes with a circular aperture or annular aperture light barrier (transparent for the interaction products). In addition and as already further described, the filtering of the interaction products is carried out for each detection area by means of a detector having a plurality of mutually independent detection fields sensitive to the interaction products.

1: Particle beam system

3: Main particle beam

5: Location

7: Objects

9: Second particle beam

10: Controller

11: Particle beam path

100:Objective system

101: First plane

102:Objective lens

103: Rectangular field

200: Detector system

205: Projection lens

208: Filter device

209: Particle multi-detector

210: First step particle beam lens

211: Second step particle beam lens

211: Plane

213: Position, light bar

214: Interlaced planes

215: Detection area

215a, 215b, 215c: Detection area

215d, 215e: Detection area

216a, 216b: Detection field

217: Field

220: Central area

221, 222: Annular section

223: Annular section, peripheral area

230, 231, 232, 233, 235, 236: Further particle beam lenses

237, 234: light bar

238: First intersecting plane

239: Second interlaced plane

240, 241, 242, 244: Deflection system

300: Particle beam generation equipment

301: Particle source

303: Collimating lens

305:Multi-aperture configuration

307: Field lens

309: Divergent particle beam

311: Particle beam

313: porous plate

315: aperture

317: Central point

319: Field

323: Particle beam focus

325: Plane

400: Particle beam switch

515c, 515d: Intensity distribution

515e:Intensity distribution

600: Imaging energy filter

601: First input side plane

602: Output image plane

603: Second input side plane

604: Second output side plane

700: Distributed production components

801, 802: The first double deflection system

803, 804: Second double deflection system

803a, 803b: aperture

810:Electrified area

811, 812, 813, 814, 815, 817, 818: Detection area

811a, 812a, 818a: Detection area

901: The First Fallout

902: Collect the first interaction product

903: Second Fallout

904: Collect the second interaction product

905:Evaluation

906: Image information containing topological effects

The following is an explanation of the details of the above and further specific embodiments based on the drawings. Detailed description of the drawings: FIG1 shows a schematic diagram of a specific embodiment of a multi-beam particle beam instrument.

FIG2 shows a schematic diagram of a detector system in the first specific embodiment.

Figure 3 shows a top view of a light bar with an annular aperture.

FIG4 shows a schematic diagram of a second specific embodiment of a detector system.

FIG5 shows a schematic diagram of a further specific embodiment of a detector system.

Figure 6 shows a top view of a light bar with circular apertures.

FIG7 shows a schematic diagram of a specific embodiment of a detector system having a detector with a plurality of detection fields for each detection area.

FIG8 shows a top view of a detector having a number of detection regions containing the intensity distributions of the interaction products incident on the detection regions (shown in an exemplary manner).

FIG9 shows a top view of a detector having a number of detection regions containing the intensity distributions of the interaction products incident on the detection regions (shown in an exemplary manner).

FIG10 shows a schematic diagram of a detector system including an energy filter.

Figure 11 shows a schematic diagram of a detector system including a dispersed element.

Figure 12 shows a top view of a multiple lightbar with multiple bright field apertures and dark field apertures.

FIG13 shows a schematic diagram of a further specific embodiment of a detector system.

FIG14 shows a top view of a detector having a number of detection regions containing the intensity distribution of the interaction products incident on the detection regions when the object is charged (shown in an exemplary manner).

FIG15 shows a further top view of the detector from FIG14 with a modified allocation between detection fields and detection areas.

FIG16 shows a flow chart of a method for amplifying topological effects.

FIG. 1 is a schematic diagram of a particle beam system 1 using a plurality of particle beams. The particle beam system 1 generates a plurality of particle beams that are incident on an object to be inspected so as to generate interaction products therein, such as second electrons, which are emitted from the object and then detected. The particle beam system 1 is a scanning electron microscope (SEM) that uses a plurality of primary particle beams 3 to impact a plurality of locations 5 on the surface of an object 7 and generate a plurality of spatially spaced electron beam spots therein. The object 7 to be inspected may be of any type and may include, for example, a semiconductor wafer, a biological sample, and a configuration of miniaturized components. The surface of the object 7 is arranged in a first plane 101 (object plane) of an objective lens 102 of an objective lens system 100.

The enlarged section I1 in FIG. 1 shows a top view of the object plane 101, which contains a generally rectangular field 103 of impact locations 5 formed in the first plane 101. In FIG. 1, the number of impact locations is 25, forming a 5 x 5 field 103. For the sake of simplicity of illustration, the number of impact locations 25 is chosen to be a small number. In particular, the number of particle beams or impact locations can be chosen to be larger, such as, for example, 20 x 30, 100 x 100, etc.

In the illustrated embodiment, the field 103 of the impact locations 5 is a generally rectangular field with a constant distance _P1 between adjacent impact locations. Exemplary values for the distance _P1 are 1 micron, 10 microns or 40 microns. However, the field 103 may also have a different symmetry, such as, for example, hexagonal symmetry.

The particle beam spot diameter formed in the first plane 101 is not large, and exemplary values of the diameter are 1 nm, 5 nm, 10 nm, 100 nm, and 200 nm. The objective lens system 100 is used to focus the particle beam 3 that forms the beam spot 5.

The primary particles hit the object to generate interaction products, such as second electrons, backscattered electrons, or primary particles that undergo reverse motion due to other factors, which emerge from the surface of the object 7 or from the first plane 101. The interaction products emerging from the surface of the object 7 are formed into a second electron beam 9 by the objective lens 102. The particle beam system 1 provides a particle beam path 11 to send a plurality of second particle beams 9 to the detector system 200. The detector system 200 includes a particle optical device having a projection lens 205 to guide the second particle beam 9 to a particle multi-detector 209.

Section I2 in Fig. 1 shows a plan view of a plane 211 in which the individual detection areas of the particle multi-detector 209 are arranged, on which the second particle beam 9 impacts positions 213. The impact positions 213 are located in a field 217 at a regular distance _P2 from each other. Exemplary values of the distance _P2 are 10 microns, 100 microns and 200 microns.

The primary particle beam 3 is generated in a particle beam generating device 300, which includes at least one particle source 301 (e.g., an electron source), at least one collimating lens 303, a multi-aperture configuration 305, and a field lens 307. The particle source 301 generates a divergent particle beam 309, which is collimated or substantially collimated by the collimating lens 303 to form a particle beam 311 to irradiate the multi-aperture configuration 305.

Section I3 in FIG. 1 shows a plan view of a multi-aperture configuration 305. The multi-aperture configuration 305 includes a multi-aperture plate 313 in which a plurality of openings or apertures 315 are formed. The center points 317 of the apertures 315 are arranged in a field 319 corresponding to the field 103 formed by the particle beam spot 5 in the object plane 101. The spacing P3 between the center points 317 of the apertures 315 can have exemplary values of about 5 microns, 100 microns, and 200 microns. The diameter D of the aperture 315 is smaller than the distance P3 between the center points of the apertures, and exemplary values of the diameter D are 0.2 x P3, 0.4 x P3, and 0.8 x P3.

Particles of the irradiation particle beam 311 pass through the aperture 315 and form the particle beam 3. The plate 313 captures the particles of the irradiation particle beam 311 that hit the plate 313 and are therefore not used to form the particle beam 3.

The multi-aperture configuration 305 focuses each particle beam 3 due to the applied electric field, thus forming a particle beam focus 323 in a plane 325. By way of example, the diameter of the particle beam focus 323 can be, for example, 10 nanometers, 100 nanometers, and 1 micrometer.

The field lens 307 and the objective lens 102 provide a first imaging particle optical device for imaging the plane 325 (in which the focus is formed) on the first plane 101, so that a field 103 or particle beam spot is formed here at the impact location 5. For the extent that the surface of the object 7 is arranged in the first plane, the particle beams are formed accordingly on the surface of the object.

The objective lens 102 and the projection lens arrangement 205 provide a second imaging particle optical device for imaging the first plane 101 onto the detection plane 211. Thus, the objective lens 102 is a lens that is part of both the first and the second particle optical device, while the field lens 307 belongs only to the first particle optical device and the projection lens 205 belongs only to the second particle optical device.

The particle beam switch 400 is arranged in the particle beam path of the first particle optical device between the multi-aperture arrangement 305 and the objective system 100. The particle beam switch 400 is also a part of the second particle optical device in the particle beam path between the objective system 100 and the detector system 200.

Further information on such multi-beam particle beam systems and components used herein, such as particle sources, multi-aperture plates and lenses, can be obtained from the international patent applications WO 2005/024881, WO 2007/028595, WO 2007/028596, WO 2011/124352 and WO 2007/060017 and from the German patent applications with the application numbers DE 10 2013 016 113.4 and DE 10 2013 014 976.2, the complete disclosures of which are hereby fully incorporated by reference into the present application.

Furthermore, the detector system 200 has a filter device 208, by means of which the interaction products (e.g., electron beam 9) emitted from the object 7 or the first plane 101 are filtered according to their trajectory. Examples of detector devices with different filter devices are described in more detail below based on FIGS. 2 to 15 .

The multi-beam particle beam system further has a controller 10, which is specifically implemented for controlling the individual particle optical components of the multi-beam particle beam system and for evaluating and analyzing the detector signals obtained by the multi-detector 209. Further, the controller 10 is specifically implemented to generate an image of the surface of the object on a reproduction device, such as a display, based on the detector signals generated by the multi-detector 209.

The detector system 200 in FIG. 2 has two further particle beam lenses 210, 211, plus a projection lens 205 and a multi-detector 209. The first further particle beam lens 210 is staggered in a staggered plane 214. In this staggered plane 214, the trajectories of the interaction products leaving the first plane 101 (object plane) in different regions overlap. The second additional particle beam lens 211 is operated in such a way that its focusing plane is substantially in the staggered plane 214 of the first additional particle beam lens 210. The interaction products are emitted from many regions in the first plane 101, and then propagate behind the second additional particle beam lens 211, and are projected to many detection regions 215 of the multi-detector 209 by the projection lens 205.

A light barrier 213, with the help of which the interaction products can be filtered as required according to their individual trajectories, is arranged in or near the interlaced plane 214, i.e. between the two additional particle beam lenses 210 and 211. Two exemplary light barriers 213 are depicted in Figures 3 and 6. The light barrier 213 depicted in Figure 3 has a central region 220 and a peripheral region 223, through which the interaction products cannot pass. Between the central region 220 and the peripheral region 223, the light barrier 213 has an annular region, through which the interaction products can pass, which in the depicted embodiment consists of three annular segments 221, 222, 223. The network exists between the annular segments 221, 222, 223, separating the annular segments from each other and only serves to connect the central area 220 with the peripheral area 223. With the help of an annular light barrier, the interaction products can be filtered according to the starting angle when they emerge from the object 7 or leave the first plane 101. Therefore, only the interaction products that leave the first plane 101 within a certain angle range can pass through the light barrier in one of the three annular regions 221, 222, 223 that is transparent to the interaction products. With the help of such a light barrier, the topological contrast can be improved because the interaction products (such as second electrons) mainly emerge under larger incident angles relative to the incident partial beams on the edge of the object surface 7.

Since the light barrier 213 is arranged in a staggered plane 214 of the detector system, only a single annular light barrier is required for all partial beams of the multi-particle beam system. Thus, the interaction products generated from the object 7 by all partial beams of the particle beam system undergo the same filtering.

In the specific embodiment of FIG. 2 , two further particle beam lenses 210 , 211 form a projection system together with the light barrier 213 and the projection lens 205 .

The light barrier 213 in FIG6 has only one circular aperture 214 through which the interaction products can be transmitted. By means of such a "bright field light barrier" in the staggered plane 214 of the detector system 200 in FIG2, interference of the detection signals between the detection areas of the detector 209 can be avoided. When an interaction product emanating from a field area in the first plane 101 hits a detection area 215 not assigned to this field area, interference between the detection areas 215 can be established. With the aid of the bright field light bar 213 in FIG. 6 , it can be determined by a suitable choice of the aperture diameter of the circular aperture 214 that all interaction products which, due to their trajectory, should impinge on a detection region independent of the corresponding field region have been filtered out and absorbed by the light bar 213. The trajectories of these interaction products, which when emitted from the object already combine a large start angle and a large start energy, extend in the outer region of the intersecting plane with respect to the radial direction. The use of a bright field light bar reduces interference between adjacent particle beams. Furthermore, the contrasts, such as edge contrasts, are affected by a bright field light bar.

In order to produce different filtering effects, the light bars 213 are arranged in the detector system 200 in an interchangeable manner, and a plurality of light bars with different aperture diameters, ring diameters and ring widths can be provided. Instead of an interchangeable light bar containing only one light bar aperture, a plurality of light bars can also be used. FIG. 12 depicts a plan view of a multi-light bar 803 containing a plurality of light bar apertures 803a-803d. In the multi-light bar depicted in FIG. 12, each of the two light bar apertures 803a, 803b has an annular aperture transparent to the interaction products, wherein the inner diameter and the outer diameter of the annular apertures are different. The two further light bar apertures 803c, 803d are circular and have different aperture diameters. However, there may be other light bar configurations with more, fewer, or different light bar apertures.

FIG. 13 shows an exemplary embodiment with a detector system, the design of which is similar to that of FIG. 2 . The detector system again comprises a first additional particle beam lens 210, which generates an interlacing in an interlacing plane. A second additional particle beam lens 211 again operates in such a way that its focusing plane substantially overlaps the interlacing plane formed by the first additional particle beam lens 210. The interaction products are emitted from a plurality of regions in the first plane 101, and then propagate behind the second additional particle beam lens 211, respectively, and are projected to a plurality of detection regions 215 of the multi-detector 209 by means of a projection lens 205. In addition to the exemplary embodiment of FIG. 2 , in the exemplary embodiment of FIG. 13 , a first double deflection system 801, 802 is arranged between the first additional particle beam lens 210 and the interlaced plane, and a second double deflection system 803, 804 is arranged between the interlaced plane and the second further particle beam lenses. As in the exemplary manner depicted in FIG. 12 , a multi-light barrier 803 is arranged in the interlaced plane. With the aid of the two double deflection systems 801, 802, 803, 804, one of the apertures of the multi-light barrier 803 can be selected in this exemplary embodiment, wherein only two apertures 803a, 803b of the multi-light barrier are depicted in FIG. Therefore, depending on its activation, with the help of the dual deflection systems, it is possible to switch between different contrasts with the help of the multi-light bar. Therefore, the two dual deflection systems 801, 802, 804, 805 act as aperture selectors.

In the specific embodiment of FIG. 13 , two further particle beam lenses 210 and 211 form a projection system having a light barrier 213, a double deflection system 801, 802, 804, 805 and a projection lens 205.

In addition to the projection lens 205 and the multi-detector 209, the detector system 200 in FIG4 has six further particle beam lenses 230, 231, 232, 233, 235, 236. The two first further particle beam lenses 230, 231 form a first interlacing in a first interlacing plane 238, and the two subsequent further particle beam lenses 232, 233 form a second interlacing in a second interlacing plane 239. The two further particle beam lenses 235 and 236 then recollect the particle beams of the interaction products emitted from the second interlaced plane 239 at the second interlaced plane 239, and thus, with the help of the projection lens 205 on the multi-detector 209, the interaction products emitted from the many field regions in the first plane 101 are projected onto the many detection regions 215 of the multi-detector 209 again.

In this embodiment of the detector system 200, two different light bars 237, 234 can be used simultaneously in the first and second interlaced planes 238 and 239. By way of example, the bright field light bar 213 depicted in FIG. 6 can be arranged in the first interlaced plane 238, and the light bar with an annular aperture depicted in FIG. 3 can be arranged in the second interlaced plane 239. At the same time, in this embodiment, suppression of interference between the detection area 215 according to the starting angle in the first plane 101 and the target filtering of the interaction products is performed.

Here, attention is focused on the fact that the two light bars 237, 234 can also be arranged in an interchangeable manner, so that a light bar with an annular aperture is arranged in the first intersecting plane 238, and a light bar with a central aperture is arranged in the second intersecting plane 239.

By changing the excitation of the further particle beam lenses 230, 231, 232, 233, 234, 235, the trajectories of the interaction products in the two intersecting planes 238, 239 can be set independently of each other. By changing the trajectories in the intersecting planes 238, 239, different beam radii and beam diameters can be simulated, so that the beams do not need to be exchanged mechanically. When entering the detector system 200 and when entering the projection lens 205, the trajectories can in this case remain constant, so that the correlation between the field areas in the first plane 101 and the detection areas of the multi-detector 209 can be maintained. The object field transmitted by all particle beams of the interaction products in the first plane 101 remains constant and remains constant during the process.

In this case, the particle beam lenses 230, 231, 232, 233, 235, and 236 may be magnetic lenses or electrostatic lenses.

In the specific embodiment of FIG. 4 , six further particle beam lenses 230, 231, 232, 233, 235, 236 and two light barriers 234, 237 together with the projection lens 205 form a projection system.

The specific embodiment of the detector system 200 in Figure 5 has a design very similar to the detector system 200 in Figure 4. In particular, the detector system 200 in Figure 5, in addition to the projection lens 205 and the multidetector 209, again has a total of six further particle beam lenses 230, 231, 232, 233, 235, 236, between which the first two further particle beam lenses 230, 231 again produce a first interlacing in a first interlacing plane 238, and the two subsequent further particle beam lenses 232, 233 again produce a second interlacing in a second interlacing plane 239. In addition to the specific embodiment in Fig. 4, the detector system 200 in Fig. 5 has in each case one deflection system 240, 244 respectively before the first interlacing plane 238 and after the first interlacing plane 238. The detector system 200 also has one deflection system 241, 242 respectively before and after the second interlacing plane 239. As a result of the different activation of the deflection systems respectively before and after the respective interlacing plane 238, 239, with a light bar 237, 234 in between, edge effects of the signals detected by the multi-detector 209 can be amplified and a shadow effect can be produced. The key point here is that the deflection experienced by the particle beams of the interaction products by the deflection systems 244, 241 respectively arranged before the stagger plane is compensated again by the deflection systems 240, 242 arranged after the respective stagger plane. Since the stagger planes between the two deflection systems are respectively aligned with each other, this means that the deflection systems 244, 241 arranged before the stagger plane and the deflection systems 240, 242 arranged after the same stagger plane can produce consistent deflections under a specific configuration.

By recording a plurality of images with different deflection angles in the interlaced planes and by evaluating the individually occurring shading effects in a controller 10, a 3D data record of the sample surface can be generated.

The deflection systems 240, 244, 241, 242 can be implemented as a single deflection system or a dual deflection system, respectively, but a single deflection system is sufficient for most applications.

In the specific embodiment of FIG. 5 , six further particle beam lenses 230, 231, 232, 233, 235, 236 together with two light barriers 237, 238, deflection systems 240, 244, 241, 241 and projection lens 205 form a projection system.

FIG7 shows a top view of a further specific embodiment of a multi-detector 209 of a detection system. This detector 209 also has an associated detection area 215a, 215b, 215c for each field area in the plane 101. However, in this detector 209, each detection area 215a, 215b, 215c is again divided into a plurality of detection fields 216a, 216b, which are detected independently of each other. In FIG7, only one column of the detection areas 215a, 215b divided into detection fields 216a, 216b for detecting independently of each other is depicted, including detection areas 215b and 215c. Furthermore, FIG. 7 depicts 20 detection fields 216a, 216b for each detection region 215b, 215c, respectively. However, the number of detection fields 216a, 216b in each detection region 215b, 215c may also be different; in particular, more or fewer detection fields may be present in each detection field. The number of detection fields in each detection region preferably lies in the range of 3 to 64. A quadrilateral or hexagonal configuration of the detection fields is possible, but other symmetries are also possible. In cases where a high measurement speed is not important, the number of detection fields in each detection region may also be significantly greater.

In this specific embodiment of the detector system 200, the output signals of the detection fields 216a, 216b belonging to the same detection area 215b, 215c are not taken into account for the image generation in the subsequent evaluation by the controller 10, or the output signals of many detection fields belonging to the same detection area are combined with each other in a suitable manner by calculation of the controller 10, and only when the corresponding interaction products hit the multi-detector 209 are they filtered according to their individual trajectories.

A corresponding multi-detector 209 containing a plurality of detection fields 216a, 216c per detection region 215a, 215b, 215c can be implemented in many different ways. A first embodiment of such a multi-detector 209 can be a CCD camera with an upstream scintillator. Each pixel of the CCD camera then forms a detection field 216a, 216b, and the plurality of detection fields together then form a detection region 215a, 215b, 215c, respectively. In other embodiments, an optical fiber cable that transmits light generated by the interaction products impinging on the scintillator can be arranged between a scintillator and a detector. The optical fiber cable then has at least one optical fiber for each detection field 216a, 216b. And the detector similarly has a dedicated detector or a dedicated detector pixel for each detection field. However, in addition, a corresponding detector 209 can also be a very fast pixel electron detector, which directly converts the incident electron (interaction product, second electron) into an electrical signal. In this case, each detector pixel also forms a detection field. The specific embodiments described can also be combined. By way of example, the optical fiber cable arranged after the scintillator can be guided to a first group of detectors, each detection area in the group having only a single detector. By means of a beam splitter arranged between the scintillator and the fiber optic cable entry, the other part of the light generated in the scintillator can be directed to a second group of detectors, each detection area of which has a plurality of detectors. Each detector associated with the same detection area then forms a detection field. Since both groups of detectors have completely different numbers of detectors, the two groups of detectors can be read using the corresponding different clocks of the entire detector group. Since the second group of detectors generally has a lower clock due to the larger number of detectors, signals that do not require a high data rate, such as the signal of the particle beam conditioning assembly, can be obtained, while the first group of detectors can be used to obtain the signal used for the image generation.

FIG8 and FIG9 respectively depict further plan views corresponding to the multi-detector 209, and simultaneously indicate the intensity distribution of the individual particle beams of the interaction products incident on the individual detection regions within the detection regions.

If the objective lens 102, the beam switch 400 and the projection lens 205 are absolutely aberration-free, and if the object surface is planar and charge-free, the interaction products emitted from each field region in the plane 101 should be projected onto the detector 209 by the system consisting of the objective lens, the beam switch 400 and the projection lens 205, so that the intensity distribution in each detection region 215 is rotationally symmetric, as shown in the intensity distribution 515e in a detection region 215e in Figure 8. However, due to many effects, the actual intensity distribution incident on individual detection regions will deviate from this ideal condition. By way of example, such effects can be topological effects of the object surface, which influence the starting conditions of the second electrons emitted from the object, or simply charge effects. Furthermore, intensity distributions that deviate from rotational symmetry can occur in the detection regions due to aberrations in the objective 102, the beam switch 400 and the projection lens 205. This is represented in FIG9 by the interlaced lines 515a in the detection region 215a. If the aberrations that cause deviations from the rotational symmetry are known in the ideal focus situation, this information can be used to generate an autofocus signal. For this purpose, the interaction products detected in the individual detection fields of the same detection region and the detector signals emitted therefrom can be analyzed with respect to the spatial distribution. If the constructed intensity distribution symmetry deviates from a known desired shape, adjustments such as refocusing are required. When the symmetry of the intensity distribution within a detection region has the desired shape, ideal focusing has been achieved. The global displacement or deformation of the intensity distribution of the interaction products on the detector relative to the desired position or desired distribution allows conclusions to be drawn about the overall sample appearance, such as, for example, a sample collage or an overall sample charge. Here, sample properties are global properties if they extend beyond the field region of an independent particle beam.

If a major partial beam hits the edge of the object surface in the first plane 101, this generally results in a displacement of the intensity distribution in the plane of the multidetector 209 and a change in the shape of the intensity distribution due to different trajectories of the interaction products emanating from the sample. This is indicated in FIG8 for the intensity distributions 515c and 515d in the sections 215c and 215d. The changed form of the intensity distribution of the interaction products in the plane of the multidetector 209 results from corresponding changes in the trajectories of the interaction products due to the surface topology of the object or due to other factors, such as, for example, local changes. By evaluating the detection signals recorded with the individual detection sites, it is again possible to determine the intensity distribution displacements of the detected interaction products, as well as the deviations of the intensity distribution from the rotational symmetry. By evaluating this additional information, the image information subsequently presented to the user can be improved, for example by highlighting edges.

In particular, in the reflection mode, the local start angle of the second electron is inferred from the positions determined on the detector. The advantage is that this evaluation can be performed multiple times per image (frame) and is particularly advantageous for each scan pixel. From the start angle distribution in combination with further information about the object, such as the material composition and/or the height of the topological features, the lateral shape of the features can be calculated. For this purpose, the relative position of the brightness distribution generated by the second electrons can be analyzed, and the focus at the detector, relative beam form changes and beam position changes can be analyzed.

Charging the object at the location of the primary beam impact also results in a displacement of the intensity distribution of the interaction products in the detector plane and a change in the form of the intensity distribution of the interaction products. As depicted in FIG14 , charging of the object in the charged region 810 can result in a wider intensity distribution of the interaction products in a portion of the detection region 811. In other detection regions 812, 813, 818, the intensity distribution is displaced and partially elongated relative to the case of an uncharged object, thus elongating the intensity distribution emitted in the plane of the multi-detector 209. In the other detection areas 814, 815, the relevant positions on the surface of the object are far enough away from the charged area so that the charge of the object no longer has an effect and the intensity distribution has a predetermined form and position. This makes it easy to project interference of the detection signal, especially in the detection area 817, to the intensity distribution of the adjacent detection area 812.

By evaluating the detector signals in the individual detection fields, a charge contrast image can be generated. By way of example, the specific forms on which the interaction products are detected can be depicted in a special way in the depicted image by means of these points. Furthermore, interferences can be avoided by means of the correlation between the detection regions and the assigned detection fields modified according to the intensity distribution determined by means of the detection fields. This is depicted in FIG. 15 for three detection regions 811a, 812a, 818a. The detection fields indicated by the blocks in FIG15 are determined by the intensity distributions determined locally in the individual detection regions and are combined with the new ones to form the detection regions 811a, 812a, 818a so that the individual intensity distributions of the interaction products are completely within the boundaries of each detection region. By way of example after reassignment, six detection fields are associated with the original detection region 811 in FIG14, while a detection region 812a containing ten detection fields is generated from a different original detection region 812 after reassignment. After the detection fields have been reassigned to the detection regions, the detector signals in all detection fields are then added to a signal respectively and associated to the corresponding object point on the object surface as an image signal. Optionally, the detection fields can be reassigned to the detection regions during the evaluation of the detector signals for individual image points on the object surface.

As mentioned above, charging or excessive edge contrast can lead to interference (interference between the detector channels) in a multi-detector with a single fixed detection area for each image region, because a portion of the detection signals is no longer uniquely associated with the detection areas. Using detectors with multiple detection fields per detection area, that is, where multiple detectors are available for each primary beam, the detection fields associated with each detection area can be re-correlated, so that continuous areas of samples with increased signal strength are found based on the use of the positions of the beams after the analysis of the beam positions, firstly reducing interference and then without loss of detector signals in other channels. It is particularly advantageous if this evaluation is not performed only once per frame, but multiple times per frame or even multiple times per pixel. As a result, the need for a possible charge compensation system or the topology requirements of the object are substantially reduced.

Especially in the case of charged objects, this method can be used to infer the local object structure within the reflection pattern, as described above.

By integrating all detector signals of all detection fields belonging to the same detection area 215a, image information can also be obtained if the object irradiation with the primary particle beam causes a local sample to be charged.

The detection system 200 in FIG. 10 has, in addition to the multi-detector 209 and the projection lens 205, a so-called imaging energy filter 600, such as an omega filter. By way of example, such an imaging energy filter is described in US 4740704 A. The imaging energy filter 600 images a first input side plane 601 in an achromatic manner into an output image plane 602. At the same time, the imaging energy filter images a second input side plane 603 in a dispersive manner into a second output side plane 604, i.e., the dispersive plane. By configuring a light barrier in the dispersive plane 604, in which the second input side plane 603 has been imaged, the energy of these interaction products that can pass through the filter 600 can be changed. What is achieved in this way is that only those interaction products emanating from the object with an energy predetermined by the beam in the dispersion plane 604 can be detected by the multi-detector 209. In this embodiment, the interaction products are also filtered according to their individual trajectories in the projection system, even if the energy filter determines the trajectory of each interaction product depending on its kinetic energy in the filter. In this embodiment, the imaging energy filter 600 together with the projection lens 205 forms the projection system.

In the manner described above, voltage contrast images can be produced using the multi-beam system because the energy of the interaction products is determined by the potential of the object at the location where the interaction products leave the object.

FIG. 11 depicts a detector system 200 which, in addition to the multi-detector 209 and the projection lens 205, also has a dispersion generating element 700. By way of example, such a dispersion generating element can be a magnetic sector. The interaction products entering the dispersion generating element 700 are separated in the dispersion generating element 700 according to their kinetic energy. In this case, the multi-detector 209, such as the one in FIG. 7 , has a number of detection fields 216 a, 216 b for each detection region. Then, due to the dispersion in the dispersion generating element 700, the interaction products emanating from each field region in the plane 101 hit different detection fields 216 a, 216 b of the same detection region 215 b. After suitable evaluation of the detector signals within a number of detection fields, image information can again be obtained, which depends on the kinetic energy of the interaction products detected within the individual detection field. Since the kinetic energy of the interaction products then depends on the electrostatic potential at the location where the interaction products leave the first plane 101, voltage contrast images can be generated in this way.

By evaluating the distribution of the signals within the detection fields belonging to the same detection area, conclusions can be drawn about the adjustment state of the overall system. These conclusions or this information can be used to readjust the system in an automatic manner or to initiate automatic adjustment actions. The evaluation of the distribution form or the deviation of the signals within the detection fields belonging to the same detection area can also be used to draw conclusions about focusing and other parameters, such as the tilt of the object surface. Alternatively or additionally, the distribution of the signals within the detection fields belonging to the same detection area can be averaged over a plurality of detection fields and/or in time. This then provides information about overall object properties, such as the overall tilt of the object surface relative to the optical axis of the particle beam system.

FIG. 16 illustrates a method that can be performed using a particle beam instrument and by obtaining image information containing an amplified topological effect of the object surface. In a first step, a plurality of mutually separated field regions in the object surface are irradiated with a primary particle beam of charged particles. In this step 902, interaction products emitted from the object due to the incident primary particle beam are collected by means of a first absorption field, and the interaction products collected by the first absorption field are projected onto a plurality of detection regions of a detector, so that the interaction products emitted from two different field regions are projected onto different detection regions of the detector. Thereafter, in a further step 903, a plurality of mutually separated field regions in the object surface are irradiated simultaneously with the primary particle beam of charged particles. In step 904, the interaction products emitted from the object due to the incident primary particle beams are collected by means of a second suction field, wherein the second suction field is different from the first suction field. Here, the interaction products collected by the second suction field are sequentially projected onto a plurality of detection areas of a detector, so that the interaction products emitted from two different field areas of the object are projected onto different detection areas of the detector. In a subsequent step 905, the signals detected under the two different suction fields are evaluated together, and in step 906, a data signal is obtained from the detector signals obtained under the different suction fields, wherein the data signal topology effect of the object is highlighted. In this case, the two suction fields in steps 901 and 903 should be significantly different; in particular, the electric field strength of the stronger suction field should be at least 10% greater, preferably 20% greater than the electric field strength of the weaker suction field on the surface of the object. At this time, the electric field strength of the stronger suction field should be at least 100V/mm greater than the electric field strength of the weaker suction field.

1: Particle beam system

3: Main particle beam

5: Location

7: Objects

9: Second particle beam

10: Controller

11: Particle beam path

100:Objective system

101: First plane

102:Objective lens

103: Rectangular field

200: Detector system

205: Projection lens

208: Filter device

209: Particle multi-detector

211: Plane

213: Location

215: Detection area

217: Field

300: Particle beam generation equipment

301: Particle source

303: Collimating lens

305:Multi-aperture configuration

307: Field lens

309: Divergent particle beam

311: Particle beam

313: porous plate

315: aperture

317: Central point

319: Field

323: Particle beam focus

325: Plane

400: Particle beam switch

Claims (10)

A detector system for use in a multi-beam charged particle beam system, the detector system comprising: a multi-detector having a plurality of detection fields; and a controller configured to: detect a first individual intensity distribution from the detector signals of the plurality of detection fields; determine a first set of detection fields from the plurality of detection fields to form a first detection region, whereby the first individual intensity distribution is completely within the boundary of the first detection region; and assign the determined first set of detection fields to the first detection region. As in the detector system of claim 1, the controller is further configured to: detect a second individual intensity distribution from the detector signals of the plurality of detection fields; determine a second set of detection fields from the plurality of detection fields to form a second detection area, whereby the second individual intensity distribution is completely within the boundary of the second detection area; and assign the determined second set of detection fields to the second detection area. As in the detector system of claim 2, the detector signals of the plurality of detection fields are generated by the interaction product of a charged particle beam and an object in an object field in the multi-beam charged particle beam system. A detector system as claimed in claim 2, wherein the first individual intensity distribution is wider than the second individual intensity distribution. As in the detector system of claim 2, wherein the second individual intensity distribution is longer than the first individual intensity distribution. For example, in the detector system of item 4 or item 5 of the patent application scope, the number of detection fields in the first set of detection fields is less than that in the second set of detection fields. For example, in the detector system of item 1 of the patent application scope, the number of detection fields in the first set of detection fields is different from that in the second set of detection fields. For example, the detector system of item 1 of the patent application scope, wherein the plurality of detection fields are arranged in a quadrilateral or hexagonal configuration. A detector system is used in a multi-beam charged particle beam system, the detector system comprising: a multi-detector having a plurality of detection fields; a controller configured to: detect a first individual intensity distribution from the detector signals of the plurality of detection fields, detect a second individual intensity distribution from the detector signals of the plurality of detection fields, detect a third individual intensity distribution from the detector signals of the plurality of detection fields; determining a first set of detection fields from the plurality of detection fields to form a first detection region, whereby the first individual intensity distribution is completely within the boundary of the first detection region, determining a second set of detection fields from the plurality of detection fields to form a second detection region, whereby the second individual intensity distribution is completely within the boundary of the second detection region, and determining a first set of detection fields from the plurality of detection fields to form a second detection region. three sets of detection fields to form a third detection area, whereby the third individual intensity distribution is completely within the boundary of the third detection area; and assigning the determined first set of detection fields to the first detection area, assigning the determined second set of detection fields to the second detection area, and assigning the determined third set of detection fields to the third detection area; wherein the first detector signal, the third The second detector signal and the third detector signal are generated by the interaction product of a charged particle beam and an object in an object field in the multi-beam charged particle beam system; wherein the first individual intensity distribution is wider than the second individual intensity distribution and the third individual intensity distribution; and wherein the second individual intensity distribution is longer than the first individual intensity distribution and the third individual intensity distribution. A particle beam system, comprising: a multi-beam charged particle beam system; and a detector system as described in item 1, item 2, item 3, or item 9 of the patent application scope.